Add CLI support for AI Gateway analytics instrumentation

Overview

Add CLI support for AI Gateway to enable easier event and metric definition generation for the AI Gateway project.

Key Discussion Points from Epic

Current State

• AI Gateway currently has ~63 events instrumented but only ~5 event definitions are visible in metrics.gitlab.com
• This is mainly because there's no CLI support in the AI Gateway repo
• AI Gateway uses the internal_events_client and sends events directly to Snowplow without verification

Proposed Approach

Based on the epic discussion, the solution involves:

1. CLI Support - Enable the CLI to work with AI Gateway's config/events directory structure
2. Documentation & Examples - Add Python examples and documentation for AI Gateway developers
3. Enable MR Reviews - Set up analytics instrumentation review bot for AI Gateway

Technical Considerations

• AI Gateway is a Python project, so the CLI should be language-agnostic
• Event definitions should follow the convention of being stored in config/events folder
• The CLI should validate event definitions against AI Gateway's schema requirements
• Different projects may have different validation requirements (e.g., milestones may not be relevant for AI Gateway)